This application is based on German Application DE 199 55 850.7, filed Nov. 20, 1999, which disclosure is incorporated herein by reference.
This invention relates to an organosilane preparation, to a process for the production thereof and to the use thereof.
Organosilicon compounds are used in rubber technology. It is known in particular to use sulfur-containing alkoxysilanes, which make excellent coupling agents and reinforcing agents for vulcanizates of rubber compounds containing silicate fillers. These include in particular the organosilanes according to U.S. Pat. No. 3,842,111.
Reinforcing additives for rubber vulcanizates are also known which are produced from the liquid organosilanes of U.S. Pat. No. 3,842,111 and silicate fillers (DE-PS 22 55 577 and U.S. Pat. No. 3,997,356).
All the organosilanes which have so far become established in the art for the stated purpose are hydrolyzable liquids which condense on contact with gaseous or liquid water with alcohol cleavage to yield high-molecular weight polysiloxanes and may thereby lose at least some of their efficacy as reinforcing additives.
In the rubber-processing industry, auxiliary chemicals which are liquid at room temperature, thus also liquid organosilanes, exhibit serious disadvantages in comparison with solid, pulverulent auxiliary chemicals. They require greater effort with regard to storage in silos, weighing and metering. Above all, they exhibit poor miscibility in the production of compounds on roll compounders.
To compensate for these disadvantages, liquid organosilanes are mixed with pulverulent fillers, thereby to obtain pulverulent products. Although this does help, it does not constitute an optimal solution, since pulverulent products are also relatively difficult to incorporate into rubber compounds. Extended compounding times are therefore required. Dusting pollutes and contaminates the environment and machinery. It has additionally been noted that the sensitivity to hydrolysis exhibited by the silanes is not eliminated. In addition, the silanes become markedly less effective if the product is stored. This is expressed, for example, in a reduction in the final crosslinkage values with regard to rubber vulcanization.
Mixtures are also known of organosilanes of the formula 
in which:
and a filler, which are present as granular preparations and comprise 30-60 wt. % of one or more organosilanes and 70-40 wt. % of one or more carbon blacks (DE 2747277). These mixtures have the disadvantage that they comprise a relatively high fines content and a high content of the pellet fraction smaller than 0.125 mm.
The object of the present invention is to provide an organosilane preparation which does not exhibit these disadvantages.
The invention provides a granular organosilane preparation comprising a mixture of one or more organosilanes and one or more fillers, which is characterized in that it comprises a fines content of less than 2%, preferably less than 0.5%.
The organosilane preparation may comprise a content of pellets smaller than 0.125 mm of less than 2%, preferably less than 0.5%.
The silane content of the organosilane preparation according to the invention may amount to from 1 to 70 wt. %, preferably 40 to 55 wt. %, relative to the organosilane preparation. The organosilane may comprise any known organosilane, but preferably Si 69, Si 264, Si 230, Si 116, Si 216, Si 203, Si 108, Si 118, Si 208, Si 255, Si 270, Si 275, Si 75, DYNASILAN MTMO or DYNASILAN MEMO, all made by Degussa-Hxc3xcls AG, Germany.
The filler content may amount to from 30 to 99 wt. %, preferably 45 to 60 wt. %, relative to the organosilane preparation according to the invention. The filler may comprise rubber blacks or pigment blacks, preferably CORAX N 121, CORAX N 110, CORAX N 242, CORAX N 234, CORAX N 220, CORAX N 375, CORAX N 356, CORAX 347, CORAX N 339, CORAX N 332, CORAX N 330, CORAX N 326, CORAX N 550, CORAX N 539, CORAX N 683, CORAX N 660, CORAX N 774, CORAX N 765, CORAX N 650, CORAX N 762, DUREX 0, CORAX 3, CORAX 4, CORAX 9, CORAX P, PRINTEX P, CORAX S 315, CK 3, CORAX XE-1, PRINTEX L, PRINTEX L 6, CORAX L 29, PRINTEX XE2, FARBRUSS FW 200, FARBRUSS FW 2, FARBRUSS FW 2 V, FARBRUSS FW 1, FARBRUSS FW 18, SPEZIALRUSS 6, FARBRUSS S 170, FARBRUSS S 160, SPEZIALRUSS 5, SPEZIALRUSS 4, SPEZIALRUSS 4A, PRINTEX 150 T, PRINTEX U, PRINTEX V, PRINTEX 140 U, PRINTEX 140 V, PRINTEX 95, PRINTEX 90, PRINTEX 85, PRINTEX 80, PRINTEX 75, SPECIALRUxcex2 550, PRINTEX 55, PRINTEX 45, PRINTEX 40, PRINTEX 60, PRINTEX XE 2, PRINTEX L 6, PRINTEX L, PRINTEX 300, PRINTEX 30, PRINTEX 3, SPEZIALRUSS 350, PRINTEX 35, SPEZIALRUSS 250, PRINTEX 25, PRINTEX 200, PRINTEX A, SPEZIALRUSS 100, PRINTEX G, FLAMMRUSS 101, all made by Degussa-Hxc3xcls AG, described in xe2x80x9cInformation fxc3xcr die Gummiindustriexe2x80x9d (xe2x80x9cInformation for the Rubber Industryxe2x80x9d), Degussa AG, PT 39-4-05-1287 Ha and xe2x80x9cPigment Blacksxe2x80x9d Degussa AG PT 80-0-11-10 86 Ha.
Use of carbon blacks with DBP values greater than 100 ml/100 g is particularly preferred. The carbon blacks may be used in wet-pelletized or dry-pelletized form or as powder.
Moreover, silicas may be used as fillers, preferably ULTRASIL VN3, ULTRASIL VN2, ULTRASIL 3370 or ULTRASIL 7000, all made by Degussa-Hxc3xcls AG.
The present invention also provides a process for producing the granular organosilane preparation, which process is characterized in that at least one organosilane is mixed with a filler and a mixing granulator is used as the mixing device. The filler may be apportioned to the mixing granulator by means of gravimetric powder metering. The mixed material may be transported to the outlet by a spiked shaft (FIG. 1). The silane may be apportioned volumetrically or gravimetrically. The silane may be injected by means of one or more nozzles at one or more positions. The mixing temperature may be from 40xc2x0 C. to 140xc2x0 C., preferably from 60xc2x0 C. to 120xc2x0 C. The speed may vary within the range of from 100 to 1500 rpm, preferably 100 to 1000 rpm. Filler throughput may vary between 10 and 150 kg/h, preferably 20 and 80 kg/h. Power consumption may amount to from 10 to 30 A. Filler throughput for one production installation may vary between 0.5 and 1.5 t/h. The circumferential speed of the spike tips may amount to between 1 and 30 m/s, preferably between 10 and 20 m/s. The residence time of the filler in the mixing granulator may amount to between 20 and 600 seconds.
In addition to the method of injecting the organosilane, the point of injection also has a substantial influence on the quality of the preparation formed.
The mixing granulator consists of a horizontally disposed, stationary tube (stator) with a spiked shaft rotating therein. The mixing granulator conventionally comprises an inlet section, in which the starting filler is fed to the mixing granulator. In this section there is located a conveying screw which imparts an axial movement component to the filler supplied. The inlet section is followed by the granulation section proper, in which the filler agglomerates through the mechanical action of the rotating spikes and by rolling against the internal wall of the stator. After leaving the granulation section, the filler, which is now in pellet-form, reaches the outlet section and is discharged continuously from the mixing granulator.
Depending on the design of the mixing granulator, the individual sections of the mixing granulator may be of different sizes. In any case, the inlet and outlet sections should be kept as small as possible in favor of the granulation section. Once the pulverulent starting filler has entered the granulation section, agglomeration of the filler begins and is complete at the end of this section. To ensure that the organosilane is distributed as homogeneously as possible over the total cross section of the filler pellets, it is necessary to spray the organosilane over the filler in the first third of the granulation section. Introduction of the organosilane at a later stage of pellet formation leads to a non-homogeneous filler pellet structure and thus to reduced pellet hardness.
To incorporate the organosilane into the filler even more homogeneously, a plurality of spray nozzles may be used for spraying, which are distributed about the circumference of the stator in a plane perpendicular to the spiked shaft. The number of nozzles may appropriately be two to five. The nozzles are arranged in a plane perpendicular to the spiked shaft, to ensure good incorporation homogeneity.
The small distance between the spike tips and the internal wall of the stator allows deposits to be prevented to the greatest possible extent. In this way, the silane may be distributed more homogeneously on the filler.
The granular organosilane preparation according to the invention advantageously exhibits better pneumatic conveying, better silo storage properties and better incorporability into rubber than known organosilane preparations.